This invention relates generally to cylindrical lasers, and more particularly, relates to a combustor used in a gain generator assembly used in the cylindrical laser to produce a lasing gas.
One particular prior art gain generator with a combustion chamber therein is shown in U.S Pat. No. 4,453,914, entitled "Low Heat Loss Laser Combustion Chamber", and is incorporated herein.
This prior gain generator has a plurality of primary rings which are combined to form a cylindrical shaped cavity. End caps attached to the primary rings and a laser housing enclose the cylindrial cavity forming a combustion chamber without a centerbody or struts therein as in prior devices. The primary ring combines the primary injectors and primary nozzles and has fluid channels formed therein for carrying fuel and oxidizer premixed with diluent therein to the primary injectors. The fuel and oxidizer with diluent mixed therein are injected by the primary injectors toward the centerline of the combustion chamber where they react forming reaction products. Because of increased pressure and temperature a counter flow of reaction products is set up such that the products flow past the primary nozzles which are a functional part of the primary rings and past the secondary injector array into a lasing cavity where additional compositions are injected by the secondary injector array. Fuel and oxidizer are routed to the gain generator assembly through supply manifolds to the primary ring feed/support struts. Upon entering the primary ring the fuel and oxidizer are used to cool the ring through channels appropriately placed near heated surfaces. Fuel and oxidizer distribution manifolds in the primary rings cause the fuel and oxidizer to be expelled from the primary injectors into the combustion chamber in a controlled manner. A laser cavity fuel feed manifold supplies fuel to the secondary injector array. The gain generator assembly is mounted in a cylindrical cavity of the laser housing.
Because of the inherent dangers in handling large quantities of fluorine, NF.sub.3 is used in most chemical lasers as a fluorine-atom generating source. A stream of NF.sub.3, premixed with a diluent (usually helium) and a stream of H.sub.2 (or other fuel, also premixed with a diluent) are introduced through separate injectors into a combustor chamber where they are mixed. The final precombustion mixture is NF.sub.3 rich so that after combustion flourine atoms will be present for use in a downstream chemical laser reaction process (F+D.sub.2 .fwdarw.DF*+H). NF.sub.3 -H.sub.2 combustion is triggered by some suitable initiator--spark, flash, fluorine precursor, or heat source The reaction is sufficiently exothermic to raise the temperature in the combustor considerably--the exact final temperature depending on several factors, including residence time and diluent to fuel ratio. The concentration of F atoms thus generated depends on both kinetic parameters and thermodynamic ones. Thermodynamic constraints in turn depend on temperature and pressure; kinetic constraints depend on both of these and also on residence time and mixing conditions. One of the most decisive factors in determining final F concentration is the plenum temperature. In general, the higher the temperature, the higher the possible F atom concentration. And, in turn, the lower the diluent concentration, the higher the temperature. The useful final diluent concentrations are sufficiently high that the F atoms produced are far fewer than could be generated in a diluent-free system.